Power supply devices that convert an input DC power into an AC power using switching elements are known. Such a power supply device transforms the convened AC power voltage using a transformer. A circuit on a secondary winding side of the transformer includes a rectifier that rectifies an AC power to be induced by the secondary winding. In such a power supply device, when a direction of a current flowing in the secondary winding is changed, a surge voltage is generated in the rectifier due to leakage flux and the like on the primary winding side and the secondary winding side of the transformer. For example, technology of absorbing the generated surge voltage using a surge absorption circuit connected to the rectifier is disclosed in, for example, Patent Document 1.
Additionally, such power supply devices include a synchronous rectification DC-DC converter that performs, using an FET (Field Effect Transistor), synchronous rectification on the AC power to be induced in a secondary winding. A choke coil is connected to an output of the synchronous rectification DC-DC converter. In a case where a battery is connected to an output terminal of such a synchronous rectification DC-DC converter, a voltage of the battery becomes higher than an output voltage of the synchronous rectification DC-DC converter in some cases. In a case where the voltage of the battery becomes high, backflow occurs in a direction from the battery toward the choke coil and the FET.